Fertilizers, Pesticides & IPM Review Notes

Fertilizers, Pesticides & IPM Review Notes

Fertilizers: Used to replace lost organic matter/nutrients in soil.

Controlling Pests with Pesticides – estimated 1/3 of the potential harvest and 1/10 of the harvested crop are lost to pest

□Farms are in the early stages of ecological succession (+fertilizers and water)  Good place for weeds (competition with crops for resources)

□Pesticide: substance that kills/controls the pest population (insecticides = insects, herbicides = plants/weeds)

• 1st generation: natural chemicals from plants
• 2nd generation: synthetic, created specifically for a pest
• Broad spectrum: Designed to kill many different types of pests
• Selective: Designed to kill a narrower range of organisms

□Persistence: Length of time they remain deadly in the environment for years, magnified in food webs (biomagnification)

□Bioaccumulation: Pesticides found built up over time in fatty tissue of predators (things that eat the insects/weeds sprayed with pesticides)  Can lead to high pesticide concentrations in the higher tropic levels (biomagnification)

□Resistance: pest populations evolve resistance over time

• Pesticide treadmill: Cycle of pesticide development followed by pest resistance, followed by development of new pesticide (positive feedback loop!)

History of Pesticides

Pre-Industrial Revolution: slash & burn agriculture, planting aromatic herbs to repel insects

Modern science-based agriculture: looked for chemicals that would reduce the abundance of pests (original ones, like arsenic, killed everything)

Developed artificial organic compounds like DDT (broad spectrum)  some compounds like Aldrin (used to control termites) found in human breastmilk

Return to biological/ecological knowledge

• Biological control: Use of natural predators/parasites to control pests  proven safe and effective!

Integrated Pest Management

• Uses a variety of methods: biological control, chemical pesticides (limited use), crop planting methods (no-till/low till to build levels of natural pest enemies, crop rotation, intercropping, pest resistant crop varieties, creating habitats for predators)
• Goal: Control, but never complete elimination of pests. More cost effective and also does less damage to the ecosystem, soil, water, air.
• World pesticide use exceeds 2.5 billion kg. (US > 680 million kg)
• $32 billion worldwide, $11 billion in US
• Once applied can decompose in place (takes a long time) or be carried by wind/water
• Breakdown products can be toxic